Shape-Selective Alkylation of Naphthalene over Zeolites: Steric Interaction of Reagents with Zeolites

Supramolecular interaction of Moxifloxacin and β-cyclodextrin spectroscopic characterization and analytical application

The supramolecular interaction of Moxifloxacin (Moxi) and β-cyclodextrin (β-CD) has been examined by UV-VIS, FTIR, H(1)NMR, SEM and fluorescence spectroscopy. The formation of inclusion complex has been confirmed on the base of changes of spectroscopy properties. The results showed that β-CD reacted with Moxi to form an inclusion complex. The Moxi and β-CD complex formed a host-guest complex in 1:1 stoichiometry and inclusion constant (K=3.95×10(2) L mol(-1)) was ascertained by the typical double reciprocal plots. Furthermore, the thermodynamic parameters (ΔH°, ΔS° and ΔG°) associated with the inclusion process were also determined. Based on the significant enhancement of the fluorescence intensity of Moxi produced through complex formation, a simple, accurate, rapid and highly sensitive spectrofluorometric method for the determination of Moxi in pharmaceutical formulation was developed. The measurement of relative fluorescence intensity was carried out at 464 nm with excitation at 289 nm. The factors affecting the inclusion complex formation were studied and optimized. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.99973) were in the concentration range of 10-60 ng/mL for spectrofluorimetry. The limit of detection (LOD) was found to be 1.6 ng/mL. The proposed method was successfully applied to the analysis of Moxi in pharmaceutical preparation.

Photodegradation of moxifloxacin in aqueous and organic solvents: a kinetic study

The kinetics of photodegradation of moxifloxacin (MF) in aqueous solution (pH 2.0-12.0), and organic solvents has been studied. MF photodegradation is a specific acid-base catalyzed reaction and follows first-order kinetics. The apparent first-order rate constants (kobs) for the photodegradation of MF range from 0.69 × 10(-4) (pH 7.5) to 19.50 × 10(-4) min(-1) (pH 12.0), and in organic solvents from 1.24 × 10(-4) (1-butanol) to 2.04 × 10(-4) min(-1) (acetonitrile). The second-order rate constant (k2) for the [H(+)]-catalyzed and [OH(-)]-catalyzed reactions are 6.61 × 10(-2) and 19.20 × 10(-2) M(-1) min(-1), respectively. This indicates that the specific base-catalyzed reaction is about three-fold faster than that of the specific acid-catalyzed reaction probably as a result of the rapid cleavage of diazabicyclononane side chain in the molecule. The kobs-pH profile for the degradation reactions is a V-shaped curve indicating specific acid-base catalysis. The minimum rate of photodegradation at pH 7-8 is due to the presence of zwitterionic species. There is a linear relation between kobs and the dielectric constant and an inverse relation between kobs and the viscosity of the solvent. Some photodegraded products of MF have been identified and pathways proposed for their formation in acid and alkaline solutions.

AN IMPROVED QSPR STUDY OF REVERSE FACTOR OF NANOPARTICLES IN ROADSIDE ATMOSPHERE ON KERNEL PARTIAL LEAST SQUARES AND GENETIC ALGORITHM

Thermal desorption-comprehensive two-dimensional gas chromatography high-resolution time-of-flight mass spectrometry (TD–GC × GC–HRTOF-MS) is one of the most powerful tools in analytical nanoparticle compounds. Genetic algorithm and partial least square (GA-PLS) and kernel PLS (GA-KPLS) models were used to investigate the correlation between reverse factor (RF) and descriptors for 50 nanoparticles fraction with a diameter of 29–58 nm in roadside atmosphere which obtained by TD–GC×GC–HRTOF-MS. The correlation coefficient leave-group-out cross validation (LGO-CV (Q2)) of prediction for the GA-PLS and GA-KPLS models for training and test sets were (0.761 and 0.718) and (0.825 and 0.814), respectively, revealing the reliability of these models. This is the first research on the quantitative structure-property relationship (QSPR) of the nanoparticles in roadside atmosphere using the GA-PLS and GA-KPLS.